Gas scrubbers are used in many industrial processes and applications to clean, remove or “scrub” certain undesirable gaseous components from gas streams in general. One area in which a large number of developments have been made is in the scrubbing of gases produced during, or related to, oil and gas recovery and storage operations. Examples of operations where a gas scrubber is typically used include loading and transportation of sour liquids, venting storage tanks during completion operations and well testing, purging of vessels and pipelines, bleeding off wellheads, venting settling tanks for underbalanced drilling, controlling emissions and odors from industrial processing, controlling vacuum truck emissions and odor control during plant turn-around and tank cleaning operations.
During such operations, poisonous hydrogen sulfide (H2S) present presents a health hazard to workmen in the area. To protect the workmen and the public-at-large, the permissible conditions and levels for emissions of hydrogen sulfide are regulated by various regulatory agencies.
Conventional systems for the absorption or removal of unwanted contaminants from a gas source or stream often employ a liquid solvent or scavenger to “scavenge” out the H2S. An example of such a treatment liquid is the hydrogen sulfide scavengers HSW705 and HSW700 manufactured by Baker Petrolite of Sugar Land, Tex., U.S.A. Information supplied by Baker Petrolite notes that the HSW705 formulation is specifically designed to remove hydrogen sulfide from produced gas and that this liquid product combines with hydrogen sulfide (H2S) to form stable, water-soluble reaction products that may be easily removed from the system. Baker Petrolite recommends that the point of injection of the scavenging chemical be as early as conveniently possible in the producing system to maximize contact time, i.e. injection downhole or before wellhead chokes are generally the best points of application. However, this may be impractical in some of the operations noted above, such as during the loading and transportation of sour liquids, venting storage tanks during completion operations and well testing, purging of vessels and pipelines, venting settling tanks for underbalanced drilling, controlling emissions and odors from industrial processing, controlling vacuum truck emissions and odor control during plant turn-around and tank cleaning operations.
Likewise, Am-Gas Scrubbing Systems (1989) Ltd. of Didsbury, Alberta, Canada distributes and markets chemical products under the trademark PARATENE, which are used as hydrogen sulfide scavengers for use in oilfield and industrial applications and, depending on the exact formulation, forms either water-soluble or oil-soluable by-products. Examples include PARATENE M310, PARATENE M311, PARATENE M315, PARATENE M316, PARATENE M320 and PARATENE M330.
The prior art is replete with various examples of devices and methods for the “scrubbing” of gas streams using such treatment liquids or liquid scavengers. However, none of the prior art devices provide a relatively portable device which is capable of efficiently removing gases like hydrogen sulfide quickly from large volumes of influent gas and without creating a significant amount of back-pressure. Furthermore, prior art devices have problems with liquid scavenger chemical exiting out of the devices when back-pressures are low, problems with dealing with the high gas volumes and flow rates when they are hooked up to a vacuum truck and problems with providing sufficient contact time to allow the liquid scavenger to treat the gas and remove or “scrub” the hydrogen sulfide. The present invention addresses these problems.